1. Field of the Invention
The present invention is directed toward automobile exterior temperature displays and, more particularly, toward algorithms for controlling automobile external temperature display systems.
2. Description of Related Art
Displays for showing temperatures external to an automobile are known in the art and taught by U.S. Pat. Nos. 5,737,243; 5,895,117; 5,416,728; 6,088,661; and 6,055,817. These references show various features of automobile temperature displays and should be considered informative of the general state of the art.
It has been found that the methods and algorithms known in the art suffer from several disadvantages that are apparent during certain common operating conditions. For example, problems and inaccuracies exist when the automobile is operated after being parked for a period of time in an environment that is cooler than the surrounding ambient conditions. Such a parking environment may be an underground parking garage when the ambient is a hot sunny day.
When the vehicle exits the garage, the sensed ambient temperature increases rapidly. At present, the conventional algorithm permits the temperature displayed to increase by one degree per minute (1xc2x0/min.). However, since the engine quickly becomes hot even on short drives, the temperature displayed tends to overshoot the actual ambient temperature, and the sensed and displayed temperature is eventually higher than the actual ambient temperature.
Accordingly, there exists a need in the art for an algorithm or control scheme to prevent the displayed temperature from rising too quickly in such situations.
The present invention is directed toward a method and system for removing or avoiding the problems in the art. More specifically, the present invention is directed toward a method and system that is adapted to prevent or minimize incorrect adjustment of the temperature display in response to locally elevated temperatures and disparities between sensed ambient and displayed temperatures.
In accordance with the present invention, a method for controlling an automobile exterior temperature display is provided. The method includes the steps of comparing a sensed ambient temperature to a displayed temperature and comparing a sensed automobile speed to a threshold speed. If the sensed speed is above the threshold speed and the sensed ambient temperature is more than a predetermined amount above the displayed temperature, the displayed temperature is adjusted at a first rate.
In further accordance with the present invention, the speed and temperature comparisons are continued for a predetermined period of time and, thereafter, the displayed temperature is permitted to increase at a second rate. The second rate is slower than the first rate.
In further accordance with the present invention, the step of comparing the speed of the automobile with a threshold speed further requires that the speed be maintained over the threshold speed for a predetermined period of time.